Communication of physical layer control parameters

ABSTRACT

Systems and methods are provided for transferring physical layer control information from a central access point to individual subscriber units while maintaining transparency to higher layers. Adaptation of wireline MAC protocols to wireless applications is greatly facilitated. Subscriber unit power level may be controlled from the central access point.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to digital communication systemsand more particularly to systems and methods for transferringinformation related to control of the physical layer.

[0002] A point-to-multipoint wireless communication system represents apotentially effective solution to the problem of providing broadbandnetwork connectivity to a large number of geographically distributedpoints. Unlike optical fiber, DSL, and cable modems there is no need toeither construct a new wired infrastructure or substantially modify awired infrastructure that has been constructed for a different purpose.

[0003] In order to conserve scarce spectrum, the data communicationdevices of a point-to-multipoint wireless communication system may shareaccess to a common frequency. In a typical scenario, one or morefrequency channels are allocated to downstream broadcast communicationfrom a central access point to a plurality of subscriber units. One ormore separate frequency channels are allocated to upstreamcommunications from the subscriber units to the central access point.For upstream communication, a medium access control (MAC) protocoldetermines which subscriber unit is permitted to transmit at which timeso as not to interfere with transmissions from other subscriber units.

[0004] For a given upstream frequency, the time domain is divided intoframes which are typically of equal duration. Each frame represents anindividually allocable unit in the time domain. One subscriber unittransmits in each frame. Reservations for transmission in a particularframe are made by the central access point and distributed in broadcastdownstream transmissions.

[0005] It is useful to model the design of a network as consisting ofmultiple layers. Layers are arrange in a hierarchical fashion with eachlayer being built on top of a layer below it. The lowest layer is knownas the physical layer and controls interaction with the physical medium.Each layer performs functions required by the layer above it and shieldsthe layer above it from the details of implementation. A hardware orsoftware entity implementing a given layer at a particular node of anetwork interacts with other entities of the same layer operating atother nodes in the network. Except for the physical layer, they do notinteract directly but rather via the lower level layers at theirrespective nodes. In a point-to-multipoint communication system, variousentities that implement the MAC protocol are collectively referred to asthe MAC layer. The MAC layer is directly above the physical layer.

[0006] In many point-to-multipoint communication systems including,e.g., a data over cable system, the MAC layer is responsible for otherfunctions besides coordinating the timing of upstream transmission sothat subscribers do not interfere with one another. For example, the MAClayer may be responsible for regulating the upstream power transmissionof individual subscriber units to prevent saturation of the centralaccess point receiver and to minimize interference to unintendedreceivers. In order to coordinate upstream transmission in the timedomain, it may also be necessary to establish the propagation delaybetween the central access point and individual subscriber units. Theprocess of establishing these propagation delays is known as ranging andmay be also a function of the MAC layer.

[0007] The discussion so far has concerned point-to-multipoint wirelesscommunication systems. Cable modem systems also involve access to ashared medium, the cable infrastructure. It would be desirable to simplyadopt a MAC protocol already developed for cable applications to thewireless context. One such protocol that has been developed is referredto as the MCNS protocol. The MCNS protocol is described inData-Over-Cable Service Interface Specifications, Radio FrequencyInterface Specification, SP-RFI-I04-980724, (Cable TelevisionLaboratories, 1997), the contents which are herein incorporated byreference.

[0008] A cable MAC layer like MCNS is a already implemented in low costchip sets. The operational characteristics of MCNS are well known.Higher layer protocol hardware and software has been developed tointeract with MCNS. Furthermore, it is desirable to maintain partscommonality between wireless modems and cable modems to the extentpossible. Unfortunately, many features of wireline MAC protocols are notappropriate for the wireless context. For example, a wirelesscommunication system may require much more frequent updates ofsubscriber unit power level than does a wireline system to accommodatechanges in propagation conditions. This creates an excessive processingburden on the wireline MAC processor. Also, subscriber unitsperiodically transmit to the central access point even when they have nonew information to transmit solely for the purpose of providing a powermeasurement level update. Each such transmission by a subscriber unitrequires an entire MAC frame. Frequent updates of power controlinformation necessitated by the wireless channel consume preciousbandwidth.

[0009] One solution to this problem of providing adequately frequentupstream power measurements in a system employing a wireline MACprotocol is described in the patent application entitled WIRELESS POWERCONTROL IN CONJUNCTION WITH A WIRELINE MAC PROTOCOL. In the systemdescribed there, upstream MAC frames are further subdivided intosubframes that are controlled by the physical layer rather than by theMAC layer. Some of the subframes are allocated to upstream powermeasurements. However, creating such a physical layer frame structurerequires downstream transmission of the physical layer controlinformation. For example, there must be scheduling informationtransmitted to the subscriber units to define access to the physicallayer frames.

[0010] Prior art implementations of point-to-multipoint communicationsystem downstream physical layers have focused on simply transferringinformation generated by the MAC layer from the central access MAC layerentity to one or more subscriber unit MAC layer entities. What is neededis a system that transfers physical layer control information from thecentral access point to individual subscriber units with completetransparency to the operation of the MAC layer.

SUMMARY OF THE INVENTION

[0011] In accordance with one embodiment on the present invention,systems and methods are provided for transferring physical layer controlinformation from a central access point to individual subscriber unitswhile maintaining transparency to higher layers. Adaptation of wirelineMAC protocols to wireless applications is greatly facilitated.Subscriber unit power level may be controlled from the central accesspoint via physical layer communications.

[0012] In accordance with the first aspect of the present invention, amethod for communicating data from the central access point to aplurality of subscriber units includes providing a physical layer systemat the central access point to implement digital communication betweenthe central access point and the plurality of subscriber units. Aphysical layer system implements a central access point portion of aphysical layer of the digital communication system. The method furtherincludes transferring data from a layer above the physical layer to thephysical layer system. Within the physical layer system, data is dividedinto codewords for encoding prior to transmission. Physical layermanagement information generated within the physical layer system andintended for transmission to a physical layer entity within at least oneof the subscriber units is included with at least one of the codewords.The codewords are transmitted to the plurality of subscriber units.

[0013] Further understanding of the nature and advantages of theinvention herein may be realized by reference to the remaining portionsof the specification and the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 depicts a point-to-multipoint wireless communication systemaccording to one embodiment of the present invention.

[0015]FIG. 2 is a flowchart generally describing steps of implementing adownstream physical layer in a point-to-multipoint communication systemaccording to one embodiment of the present invention.

[0016]FIG. 3 depicts elements of a central access point according to oneembodiment of the present invention.

[0017]FIG. 4 depicts elements of a subscriber unit according to oneembodiment of the present invention.

[0018]FIG. 5A depicts organization of a codeword to facilitatedownstream communication of physical layer control information accordingto one embodiment of the present invention.

[0019]FIG. 5B depicts the organization of power control informationwithin a codeword according to one embodiment of the present invention.

[0020]FIG. 5C depicts the organization of power control information foraccess requests according to one embodiment of the present invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

[0021]FIG. 1 depicts a point-to-multipoint wireless communicationnetwork 100 suitable for implementing one embodiment of the presentinvention. Network 100 includes a central access point or headend 102and multiple subscriber units 104. All communication is typically eitherto or from central access point 102. Communication from headend 102 toone or more subscriber units 104 is herein referred to as downstreamcommunication. Communication from any one of subscriber units 104 tocentral access point 102 is herein referred to as upstreamcommunication. In one embodiment, different frequencies are allocated toupstream and downstream communication. In alternate embodiments,subscriber units 104 may communicate with one another directly.

[0022] Each of one or more upstream frequencies is common to multiplesubscriber units. To prevent collisions between subscriber units inaccessing the shared medium, a medium access control (MAC) protocol isprovided. According to one embodiment of the present invention, a MACprotocol intended for data transmission over cable systems is used tocoordinate upstream communications in wireless network 100. An exemplaryMAC protocol of this type is the so-called MCNS protocol described inData-Over-Cable Service Interface Specifications, Radio FrequencyInterface Specification, SP-RFI-I04-98724, (Cable TelevisionLaboratories, 1997), the contents are herein incorporated by reference.

[0023] MCNS employs a time domain multiple access (TDMA) scheme toallocate access to the shared upstream frequency among the multiplesubscriber units 104. The entity controlling operation according to theMAC protocol at central access point 102 and subscriber units 104 isreferred to collectively as the MAC layer. This identifies theseentities as collectively representing a layer in a multi-layercommunication model. In reference to the well-known OSI multi-layermodel of data communications, the MAC layer as it is discussed herecorresponds to a lowest sublayer of the data link layer. Underneath theMAC layer is the physical layer which is responsible for transmittingand receiving bits over the wireless channel. The MAC layer implements aTDMA scheme for upstream communication. Each of one or more upstreamfrequencies is divided into a series of frames or minislots in the timedomain.

[0024] MCNS also implements other management functions related to theoperation of wireless communication network 100. For example, MCNSprovides for control of subscriber unit output power. In order tofacilitate operation of the TDMA scheme, MCNS also provides for rangingfunctions that establish the propagation delays between central accesspoint 102 and subscriber units 104. Centralized control of subscriberunit output power is necessary so that subscriber unit transmissions donot saturate the receiver at central access point 102. The rangingprocess wherein propagation delays are established is necessary so thatscheduled transmission times for individual subscriber units take intoaccount differences in propagation delay between the various subscriberunits and central access point 102.

[0025] According to the present invention, one or more aspects ofoperating wireless communication network 100 are managed by the physicallayer and are transparent to the MAC layer. These management functionsrequire downstream communication between entities operating at thephysical layer at central access point 102 and at least one ofsubscriber units 104. The transfer of this control information withinthe physical layer is then preferably transparent to the MAC layer andother higher layers.

[0026]FIG. 2 is a flow chart generally describing steps of transferringphysical layer control information downstream according to oneembodiment of the present invention. The primary responsibility of thephysical layers is to provide a pipeline transferring data betweenentities operating above the physical layer. At step 202, data istransferred from layer above the physical layer, e.g., the MAC layer, tothe physical layer. This data may include, e.g., application data,voice, video, and/or MAC layer management data and/or any other dataexchanged between layers above the physical layer.

[0027] One embodiment of the present invention takes advantage ofsegmentation of data to facilitate transmission by the physical layer.For example to facilitate the detection and correction of errors, thephysical layer may divide data into segments known as codewords. Eachcodeword is a group of bytes representing a simultaneous input to anencoding process. An example of such an encoding process is aReed-Solomon encoding process. A Reed-Solomon encoding process acceptsas its input an input codeword and generates an output encoded codeword.Each output codeword includes the contents of the corresponding inputcodeword with an additional series of bits acting as a checksum. Thechecksum allows the corresponding decoding process to detect and/orcorrect errors caused by impairments in the communication channel.

[0028] Step 204 groups the higher layer data into codewords. Accordingto the present invention, physical layer control information may beincluded within one or more of the codewords. A special subsegment maybe provided within the codeword structure to provide space for thisphysical layer control information.

[0029] Physical control information is included in one or more codewordsat step 206. This physical layer control information may include, e.g.,power adjustment information, scheduling information for a physicallayer TDMA frame structure, and/or frequency control informationinstructing one or more subscriber units to change their transmissionand/or reception frequencies.

[0030] At step 208, the codewords are transmitted. Transmission of thecodewords from central access point 102 to one or more subscriber units104 typically involves other various analog and digital processingsteps. For example there may be further encoding steps to helpameliorate channel impairments. An orthogonal frequency divisionmultiplexing (OFDM) system may be implemented by use of the inverse FastFourier Transform (IFFT). Also digital signals will typically beconverted to analog signals and the analog signals will be upconvertedfor transmission at the appropriate radio frequency.

[0031]FIG. 3 depicts elements of central access point 102. A CPU 302coordinates overall operation of central access point 102. A MAC layerprocessor 304 implements the central access point operation of the MACprotocol for both the upstream and downstream directions. Besidescoordinating MAC layer operation, MAC layer processor 304 also acts asan interface in relaying data to and from higher layer entities at thecentral access point. In MCNS applications, central access point MAClayer processor 304 may be a BCM 3210B integrated circuit available fromBroadcom, Inc. of Irvine, Calif.

[0032] An upstream physical layer block 306 is responsible for receivingsignals from individual ones of subscriber units 104. Upstream physicallayer block 306 transfers data received from subscriber units 104 to MAClayer processor 304. Some data related to operation of the physicallayer such as power measurement information indicating received powerfor one or more subscribe units 104, propagation delay information,etc., maybe transferred directly to CPU 302 from upstream physical layerblock 306. Details of the operation of representative implementations ofupstream physical layer block 306 can be found in the patent applicationentitled WIRELESS POWER CONTROL IN CONJUNCTION WITH A WIRELINE MACPROTOCOL and in the application entitled REALTIME POWER CONTROL IN OFDMSYSTEMS.

[0033] A downstream physical layer block 308 performs transmitterprocessing and RF signal handling for a downstream channel. FIG. 3depicts a downstream physical layer block for a single downstreamchannel but block 308 may of course be duplicated for multipledownstream frequencies. Within downstream physical layer block 308, acentral access point physical layer control processor 310 receivesphysical layer control information from CPU 302 or upstream physicallayer block 306 and processes this information. For example, centralaccess point physical layer control processor 310 may receive powermeasurements for individual subscriber units received from upstreamphysical layer block 306 either directly or via CPU 302. Central accesspoint physical layer control processor 310 may then formulate poweradjustment information for controlling individual subscriber units basedon these power measurements.

[0034] In one embodiment central access point physical layer processor310 may be combined in functionality with another physical layer controlprocessor within upstream physical layer block 306 to provide overallcontrol of the physical layer for both downstream and upstreamdirections. Also, in one embodiment CPU 302 may absorb the functions ofcentral access point physical layer processor 310 and directly providephysical control layer information to be transmitted downstream. Acodeword formation block 312 accepts physical layer control informationfrom central access point physical layer control processor 310 and alsoaccepts MAC and higher layer data from MAC layer processor 304. Codewordformation block 312 forms input data into segments for furtherprocessing. In one embodiment the segments are codewords that representinput to an encoding process such as a Reed-Solomon encoding process.The present invention, however, does not require that the segments bedefined in terms of the input to an encoding process. The segments mayrepresent any division of data to facilitate processing by the physicallayer.

[0035] In one embodiment, each codeword formed by codeword formationblock 312 includes 232 bytes. Of these 232 bytes, 1 byte is used forsynchronization and 229 bytes are reserved for MAC layer and higherlayer data received from MAC layer processor 304. The remaining 2 bytesare allocated to the physical layer control information output bycentral access point physical layer control processor 310. The datagenerated by MAC layer processor 304 and included within the codewordsmay be organized in accordance with the MAC layer protocol. Theboundaries of downstream MAC layer frames need not coincide with theboundaries of codewords.

[0036] Individual downstream MAC layer frames may include addressesselecting particular intended subscriber unit receivers or indicatingthat the MAC layer frame is intended as a broadcast to be processed byall subscriber units. A Reed-Solomon encoding block 314 applies theReed-Solomon code to the input codewords to generate output codewords.Each output codeword may include the 232 bytes of the input codeword andadditionally a 20 byte checksum so that the total codeword length is 252bytes. Additional encoding block 316 may apply other encodingtechniques, e.g., convolutional coding, block coding, turbo coding, etc.A transmitter system 318 performs the other analog and digital signalprocessing steps necessary to generate an RF signal for transmission viaan antenna 320. Transmitter system 318 performs operations related tomodulation, conversion of a digital baseband signal to an analog signal,upconversion of the analog signal to intermediate frequency (IF),filtering and further processing of the IF signal, upconversion of theIF signal to a radio frequency (RF), and further amplification andfiltering of the RF signal.

[0037]FIG. 4 is a diagram of elements of a representative one ofsubscriber units 104. A CPU 402 controls overall operation. A MAC layerprocessor 404 implements subscriber unit operation of the MAC protocolfor both upstream and downstream directions and acts as a data interfaceto higher layers. In MCNS applications, subscriber unit MAC layerprocessor 404 may be a BCM 3300 integrated circuit provided by Broadcom.An upstream physical layer block 406 transmits information provided byMAC layer processor 404 to central access point 102. Upstream physicallayer block 406 may also transmit physical layer control informationprovided by CPU 402 or physical layer control information generated inresponse to input provided by CPU 402. Examples of the upstreamtransmission of physical layer control information are disclosed in thepatent application entitled WIRELESS POWER CONTROL IN CONJUNCTION WITH AWIRELINE MAC PROTOCOL and in the patent application entitled REALTIMEPOWER CONTROL IN OFDM SYSTEMS.

[0038] A downstream physical layer block 408 performs receiver signalprocessing and RF signal handling for downstream communication fromcentral access point 102. An antenna 410 collects signals received fromcentral access point 102. A receiver system 412 performs initialamplification and filtering on the received RF signals, converts the RFsignals to an intermediate frequency (IF), filters and otherwiseprocesses the IF signal, downconverts the IF signal to a basebandsignal, converts the baseband signal to a series of digital samples, andperforms other functions such as baseband filtering and demodulation. Achannel decoding stage 414 decodes to remove, e.g., convolutionalcoding, block coding, turbo coding, etc.

[0039] A Reed-Solomon decoding block 416 accepts as input individualcodewords that have been encoded according to a Reed Solomon encodingprocess. In one embodiment, these are 252 byte long codewords includingchecksum information. Reed-Solomon decoding block 416 removes thechecksum bytes and uses them to detect and correct errors in the otherbytes. The output of Reed-Solomon encoding stage 416 is a series ofcodewords that have had their checksums removed.

[0040] Each such codeword preferably includes a subsegment devoted tophysical layer control information. In one embodiment, this is the 2byte subsegment referred to in reference to codeword formation block312. A codeword segmentation block 418 divides each codeword into asubsegment containing MAC layer and higher layer information that istransferred to MAC layer processor 404, and a subsegment containingphysical layer control information that is directed to a subscriber unitphysical layer control processor 420.

[0041] Subscriber unit physical layer control processor 420 may be partof an overall physical layer control processor that controls allphysical layer operations both upstream and downstream at subscriberunit 104. Alternatively, the functionality of subscriber unit physicallayer control processor 420 may be integrated within CPU 402 andphysical layer control data from the physical layer control subsegmentof the successive codewords may be transferred directly from codewordsegmentation block 418 to CPU 402. Subscriber unit physical layercontrol processor 420 may receive power adjustment information forupstream transmission. This power adjustment information may betransferred to CPU 402. Subscriber unit physical layer control processor420 may compute a power adjustment using techniques described in thepatent application entitled POWER REGULATION USING MULTI-LOOP CONTROL.

[0042] Subscriber unit physical layer control processor 420 may alsoprocess downstream scheduling messages related to physical layerframing, wherein upstream MAC layer frames are subdivided into physicallayer frames. Subscriber unit physical layer control processor 420 mayexamine schedules received from central access point 102 to determine inwhich physical layer frames this particular subscriber unit is scheduledfor transmission. Subscriber unit physical layer control processor 420may also detect requests for upstream transmission of power measurementinformation by this particular subscriber unit. Upstream physical layertransmission operations will occur in response to the downstreamphysical layer control information received by subscriber unit physicallayer control processor 420.

[0043] There are many examples of physical layer control informationthat may be transferred within a subsegment of a codeword or asubsegment of any type of segment employed to facilitate physical layercommunication. One example is power adjustment information. The poweradjustment information may be a multibit number indicating a positive ornegative number of decibels by which the subscriber unit is to regulateits upstream transmission power. Alternatively, the power adjustmentinformation may be a raw power measurement or channel response estimatebased on subscriber unit transmissions.

[0044] Another example of the use of downstream transmission of physicallayer control information is distributing frequency coordinationinformation. In order to operate in the presence of interference, it maybe useful to periodically adjust the frequencies of upstream anddownstream operation in wireless communication network 100. Optimalfrequencies may be determined at central access point 102 by centralaccess point physical layer control processor 310 and then distributeddownstream to the various subscriber units 104. Alternatively, a hoppingcode may be distributed to subscriber units 104. Subscriber units 104may themselves then determine their frequencies of operation inaccordance with the hopping code.

[0045] Another example of physical layer control information that may betransferred downstream arises in the context of handling collisions thatoccur when multiple subscriber units transmit access requests upstreamsimultaneously causing what is known as a collision. Although datatransmission are scheduled so that individual subscriber units do nottransmit simultaneously, requests for access to the medium may collide.

[0046] Subscriber units will detect the collision and then repeat theaccess request later but to prevent further collisions the subscriberunits will delay their retransmission of access requests by units oftime known as a backoff value. The backoff value is chosen separately ateach subscriber unit according to a pseudo-random function. The input tothe pseudo random function is a parameter knows as the backoffparameter. This backoff parameter is generated at central access point102 and distributed to the individual subscriber units 104. The backoffparameter is an example of a quantity that may be distributed within thecodeword subsegment dedicated to physical layer control information.

[0047] In the system described in the patent application entitled REALTIME POWER CONTROL IN OFDM SYSTEMS, access requests originating withmultiple subscriber units are distributed among various frequencydomains subchannels as established within an OFDM system. If two or moreaccess requests collide due to simultaneous transmission on the samesubchannel, it is possible that the overall power received during theaccess request frame will saturate the receiver. It is then desirable toinstruct all of the subscriber units to reduce the power level used foraccess requests. The reduction of output power is controlled by anotherbackoff parameter which may also be distributed within the codewordsubsegment described above.

[0048]FIG. 5A depicts organization of a codeword to facilitatedownstream communication of physical layer control information. A firstsubsegment 502 includes data being transferred from MAC layer entitiesand higher layer entities at central access point 102 to correspondingentities at one or more of subscriber units 104. In one embodiment,subsegment 502 includes 229 bytes. A second subsegment 504 includesphysical layer control information. In one embodiment, second subsegment504 is prepended to the beginning of subsegment 502. It will beunderstood, however, that the information in subsegment 504 may beappended to the end of the codeword or distributed within the codewordin any way.

[0049]FIG. 5B depicts representative contents of subsegment 504 whereinpower control information is transmitted to a particular subscriberunit. A broadcast field 506 is a single bit that defines whether theinformation is being directed to a single subscriber unit or allsubscriber units. In FIG. 5B, this bit has the value 0 to indicate thatthe power control information is being directed to a single subscriberunit. An address field 508 includes a so-called primary service IDnumber. This primary service ID number is an address of an individualsubscriber unit as defined by the MAC layer. For MCNS, this ID is a 10bit number. A power adjustment field 510 holds a power adjustmentindicator. The power adjustment indicator is a 5 bit number representingthe power error in decibels. The power adjustment indicator may be apositive or a negative number and is represented in 2's complement form.

[0050]FIG. 5C depicts representative contents of subsegment 504 whereinpower control information for access requests is being broadcast to allsubscriber units. The single bit of broadcast field 506 now has thevalue 1 to indicate that the contents of subsegment 504 are intended forall subscriber units. A field 512 includes 13 reserved bits. A poweradjustment field 514 holds a power adjustment indicator representing adesired adjustment to the power level used by all subscriber units foraccess requests. This indicator has 2 bits representing the desiredpower adjustment in 2's complement form.

[0051] It can be seen that physical layer control information may betransmitted downstream from central access point 102 to subscriber units104 in a way that is transparent to higher layers. In effect a logicalcontrol channel has been created between from the central access pointphysical layer entity to the subscriber units' physical layer entities.

[0052] It is understood that the examples and embodiments describedherein are for illustrative purposes only and various modifications arechanges in light thereof will be suggestive to persons skilled in theart and are to be included within the spirit and pervue of thisapplication and scope of the appended claims. For example, the presentinvention may be applied to wireline systems. All publications, patents,and patent applications cited herein are hereby incorporated byreference.

What is claimed is:
 1. In a point to multipoint communication system, asubscriber unit comprising: a receiver system that receives a pluralityof data segments from a central access point; and a data segmentationblock that extracts from at least one of said data segments, first dataand second data, said first data being transferred to a system withinsaid subscriber unit implementing a layer above a physical layer of saidcommunication system, said second data comprising physical layer controlinformation.
 2. The subscriber unit of claim 1 wherein said receiversystem comprises a decoding block that decodes said data segmentsindividually according to an decoding scheme.
 3. The subscriber unit ofclaim 1 wherein said at least one data segment comprises a firstsubsegment comprising said first data and a second subsegment comprisingsaid second data.
 4. The subscriber unit of claim 1 wherein said secondsubsegment further comprises an identifier indicating an intendedrecipient of said physical layer control information.
 5. The subscriberunit of claim 1 wherein said physical layer management informationcomprises a collision back off parameter.
 6. The subscriber unit ofclaim 1 wherein said physical layer management information comprises ascheduling message for allocating access to physical layer frames withina MAC layer frame.
 7. The subscriber unit of claim 1 wherein saidphysical layer control information comprises power adjustmentinformation.
 8. The subscriber unit of claim 1 wherein said physicallayer control information comprises a frequency adjustment command. 9.The subscriber unit of claim 1 wherein said first data comprises MCNSdata.
 10. In a point to multipoint communication system, a method foroperating one of a plurality of subscriber units to receive data from acentral access point: receiving a plurality of segments from saidcentral access point; dividing data received within one of segments intoa first subsegment and a second subsegment; transferring data withinsaid first subsegment to a protocol entity implementing a layer above aphysical layer; and transferring data within said second subsegment to aphysical layer control processor.
 11. The method of claim 10 whereinsaid segments are codewords representing groupings of data encodedtogether prior to transmission according to an encoding scheme.
 12. Themethod of claim 11 wherein said encoding scheme comprises a Reed-Solomonencoding scheme.
 13. The method of claim 10 wherein said data withinsaid second subsegment comprises an address of said one subscriber unit.14. The method of claim 10 wherein said data within said secondsubsegment comprises a power adjustment command.
 15. In a point tomultipoint communication system, a method for operating a central accesspoint to transmit data to a plurality of subscriber units, said methodcomprising: at said central access point, transferring first data froman entity implementing a layer above a physical layer to said physicallayer; forming data segments for transmission wherein at least one ofsaid segments comprises a first subsegment and a second subsegment, saidfirst subsegment comprising said first data and said second subsegmentcomprising control data generated within said physical layer;transmitting said data segments from said central access point.
 16. Themethod of claim 15 wherein transmitting comprises: encoding saidsegments individually according to an encoding scheme.
 17. The method ofclaim 15 wherein said control data comprises a power adjustment command.18. The method of claim 15 wherein said control data comprises a poweradjustment command to control power of access requests.
 19. In a pointto multipoint communication system, a central access point comprising: aMAC layer system implementing a MAC layer protocol of said communicationsystem; a physical layer control processor that generates physical layercontrol information; and a segment formation bloc that generates datasegments to be transformed into signals to be transmitted via atransmission medium, at least one of said data segments including bothdata received from said MAC layer system and said physical layer controlinformation.
 20. The central access point of claim 19 wherein said MAClayer protocol comprises MCNS.
 21. The central access point of claim 19further comprising an encoding block that encodes said data segmentsindividually according to an encoding scheme.
 22. The central accesspoint of claim 19 wherein said at least one data segment comprises afirst subsegment comprising said data received from said MAC layersystem and a second subsegment comprising said physical layer controlinformation.
 23. The central access point of claim 19 wherein saidsecond subsegment further comprises an identifier indicating an intendedrecipient of said physical layer control information.
 24. The centralaccess point of claim 19 wherein said physical layer managementinformation comprises a collision back off parameter.
 25. The centralaccess point of claim 19 wherein said physical layer managementinformation comprises a scheduling message for allocating access tophysical layer frames within a MAC layer frame.
 26. The central accesspoint of claim 19 wherein said physical layer control informationcomprises a power adjustment command.
 27. The central access point ofclaim 19 wherein said physical layer control information comprises afrequency adjustment command.
 28. In a point to multipoint communicationsystem, a central access point comprising: an encoding processor thatencodes a series of codewords according to an encoding scheme fortransmission to a plurality of subscriber units; and a codewordformation block that forms at least one of said codewords bycombining 1) power adjustment information controlling power of one ofsaid subscriber units and 2) application data.
 29. The central accesspoint of claim 28 wherein said encoding scheme comprises a Reed-Solomoncoding scheme.
 30. In a point to multipoint communication system, asubscriber unit comprising: a decoding processor that decodes a seriesof codewords received from a central access point according to adecoding scheme; and a codeword segmentation block that extracts from atleast one of said codewords 1) power adjustment information forcontrolling output power of said subscriber unit and 2) applicationdata.
 31. The subscriber unit of claim 30 wherein said decoding schemecomprises a Reed-Solomon decoding scheme.
 32. The subscriber unit ofclaim 30 wherein said application data comprises data formatted inaccordance with MCNS protocol.